The aeroplane pushes out over the Pacifc Ocean towards the Galápagos. Sitting near the back of the plane, I squint through parting clouds into the shimmering sea for a first glimpse of the islands - the naturalists' Mecca.

My well-thumbed second edition of Charles Darwin's Journal of Researches lies open in my lap at Chapter 17. I've spent the flight out rereading Darwin's account of his five-week journey through the Galápagos in September and October 1835 that sparked his thoughts about evolution. I compare the sketch of the main islands with the landscape now twinkling below, trying to work out which one we're passing over. I'm struck by the remarkable continuum of colour from the lowest to the highest point of each island: barren brown on the rocky shores bleeding to tropical green near the top of each volcano. The plane goes into descent. 'Diez minutos para el aterrizaje' - 'Ten minutes to landing.'

Ten years before me, a 26-year-old Swiss zoology graduate made the same two-and-a-half-hour journey from the mountainous backdrop of Quito to the stunning Galápagos Islands, some 1000 km off Ecuador's coast. It was April 1993 and Sveva Grigioni was on her way to work at the Charles Darwin Research Station (CDRS), the international body responsible for science in the archipelago, based in its main town Puerto Ayora on the central island of Santa Cruz.

The CDRS gave Grigioni two research options: she could help with some gecko work or single-handedly attempt to persuade Lonesome George, the research station's resident celebrity, to take an interest in females.

Lonesome George is the world's most famous reptile. A legend in his own long lifetime, George is thought to be the only giant tortoise from the isolated island of Pinta to have survived centuries of buccaneers and whalers in search of a square meal. Before he was discovered, the Pinta tortoise was assumed extinct. George brought hope - and thousands of tourists. But as each year comes and goes, it looks more and more like George is the only one of his kind left on earth - a symbol of the devastation man has wrought to the natural world in the Galápagos and beyond.

For Grigioni, there was no question: she chose the taciturn tortoise. 'I had the feeling that I was about to do something very important', she says.

We drop gently out of the sky. After a week in the mists and rain of Quito, it's exciting to be surrounded by sea. The wheels unfold with a clunk as the plane nears Baltra, the small central island kitted out with a runway by the US military in the Second World War. Since the 1970s, Baltra has served as the entry point for most visitors to this, the best-preserved tropical archipelago in the world.

I flip to the frontispiece of the book; from behind a crisp film of transparent paper stare the penetrating eyes of an ageing Darwin, his long, white, wise man's beard framing the lapels of a dark cloak that flows off the bottom of the page.

This is a journey I've been planning since my days as a zoology undergraduate at Cambridge. I want to see for myself the place that drew Darwin towards one of the most influential ideas in the history of science - his theory of evolution by natural selection. I want to sail into the same coves and set foot on the same beaches. I also want, I confess, to find a quiet spot beneath a cactus and read aloud from his writings, one sentence in particular: 'The natural history of these islands is eminently curious.' I love that. More than anything, this is a journey to see these same eminently curious creatures: the archipelago's extraordinary array of finches, its amphibious, algae-eating marine iguanas and of course its arcane giant tortoises.

A few days later, as we sail around the islands, a chirpy guide is regaling me and my fellow tourists about one tortoise in particular - Lonesome George. When he begins telling us about the love affair between this celebrated beast and a beautiful Swiss girl, it's clear this is one of his set pieces. He keeps a straight face, but his eyes sparkle as he describes her work to his startled audience.

If you tell an anecdote often enough, you quickly hone your routine. You embellish what works and drop what doesn't. I can't fault his delivery, but reflect that this yarn and others he tells us about George are but playful shadows of something much richer. It strikes me that this tortoise has another tale that needs to be told.

So here it is. The story of a creature that touches all who see and hear about him, an animal whose plight embodies the practical, philosophical and ethical challenges of preserving our fragile planet. The story of a conservation icon.

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About this article

Lonesome George: the life and loves of a conservation icon by Henry Nicholls

This article was published on
the Guardian website
at 10.03 EDT on Tuesday 22 August 2006.
It was last modified at 06.52 EDT on Monday 25 June 2012.
It was first published at 10.03 EDT on Tuesday 5 September 2006.